Alpha Persei

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Alpha Persei
Perseus constellation map.svg
Red circle.svg
Location of α Per (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Perseus
Right ascension 03h 24m 19.37009s[1]
Declination +49° 51′ 40.2455″[1]
Apparent magnitude (V) 1.806[2]
Spectral type F5 Ib[2][3]
U−B color index +0.38[4]
B−V color index +0.483[4]
Radial velocity (Rv)–2.04[5] km/s
Proper motion (μ) RA: +23.75[1] mas/yr
Dec.: -26.23[1] mas/yr
Parallax (π)6.44 ± 0.17[1] mas
Distance510 ± 10 ly
(155 ± 4 pc)
Absolute magnitude (MV)–5.1[3]
Mass8.5 ± 0.3[2] M
Radius68 ± 3[6] R
Surface gravity (log g)1.90 ± 0.04[2] cgs
Temperature6,350 ± 100[2] K
Metallicity [Fe/H]–0.02[7] dex
Rotational velocity (v sin i)20[8] km/s
Age41[2] Myr
Other designations
Mirfak, Mirphak, Marfak, Algeneb, Algenib, α Persei, α Per, Alpha Per, 33 Persei, BD+49 917, CCDM J03243+4951A, FK5 120, GC 4041, HD 20902, HIP 15863, HR 1017, IDS 03171+4930 A, PPM 46127, SAO 38787, WDS J03243+4952A.
Database references

Alpha Persei (α Persei, abbreviated Alpha Per, α Per), also named Mirfak,[9] is the brightest star in the northern constellation of Perseus, just outshining the constellation's best known star, Algol. α Persei has an apparent visual magnitude of 1.8,[5] and is a circumpolar star when viewed from mid-northern latitudes.

Mirfak lies in the midst of a cluster of stars named as the eponymous Alpha Persei Cluster, or Melotte 20, which is easily visible in binoculars and includes many of the fainter stars in the constellation.[10] Determined distance using the trigonometric parallax, places the star 510 light-years (160 parsecs) from the Sun.[1]


The spectrum of Alpha Persei matches a stellar classification of F5 Ib,[2] revealing it to be a supergiant star in the latter stages of its evolution. It has a similar spectrum to Procyon, though the latter star is much less luminous. This difference is highlighted in their spectral designation under the Yerkes spectral classification, published in 1943, where stars are ranked on luminosity as well as spectral typing. Procyon is thus F5 IV,[11] a subgiant star. Since 1943, the spectrum of Alpha Persei has served as one of the stable anchor points by which other stars are classified.[12]

Mirfak has about 8.5[2] times the Sun's mass and has expanded to roughly 60[6] times the size of the Sun. It is radiating 5,000[10] times as much luminosity as the Sun from its outer atmosphere at an effective temperature of 6,350 K,[2] which creates the yellow-white glow of an F-type star. In the Hertzsprung–Russell Diagram, Mirfak lies inside the region in which Cepheid variables are found.[13] It is thus useful in the study of these stars, which are important standard candles.[10]


  • Alpha Persei is the star's Bayer designation.
  • The star also bore the traditional names Mirfak and Algenib, which are Arabic in origin. The former, meaning 'Elbow' and also written Mirphak, Marfak or Mirzac, comes from the Arabic Mirfaq al-Thurayya, while Algenib, also spelt Algeneb, Elgenab, Gęnib, Chenib or Alchemb, is derived from الجنب al-janb, or الجانب al-jānib, 'the flank' or 'side'.[14][15] and was also the traditional name for Gamma Pegasi.[16] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[17] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[18] included a table of the first two batches of names approved by the WGSN; which included Mirfak for this star (Gamma Pegasi was given the name Algenib).
  • Hinali'i is the name of the star in Native Hawaiian astronomy. The name of the star is meant to commemorate a great tsunami and mark the beginning of the migration of Maui. According to some Hawaiian folklore, Hinali'i is the point of separation between the Earth and the sky that happened during the creation of the Milky Way.[19]
  • Assemani alluded to a title on the Borgian globe, Mughammid (مغمد), or Muliammir al Thurayya (ملىمرٱلطرى), the Concealer of the Pleiades, which, from its location, may be for this star.[14]
  • This star, together with δ Per, ψ Per, σ Per, γ Per and η Per, has been called the Segment of Perseus.[14]
  • In Chinese, 天船 (Tiān Chuán), meaning Celestial Boat, refers to an asterism consisting of α Persei, η Persei, γ Persei, ψ Persei, δ Persei, 48 Persei, μ Persei and HD 27084. Consequently, α Persei itself is known as 天船三 (Tiān Chuán sān, English: the Third Star of Celestial Boat.)[20]


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c d e f g h i Lyubimkov, Leonid S.; et al. (February 2010), "Accurate fundamental parameters for A-, F- and G-type Supergiants in the solar neighbourhood", Monthly Notices of the Royal Astronomical Society, 402 (2): 1369–1379, arXiv:0911.1335Freely accessible, Bibcode:2010MNRAS.402.1369L, doi:10.1111/j.1365-2966.2009.15979.x 
  3. ^ a b Arellano Ferro, A. (October 2010), "Functional relationships for T_eff and log g in F-G supergiants from uvby-beta photometry", Revista Mexicana de Astronomía y Astrofísica, 46: 331–338, arXiv:1007.0771Freely accessible, Bibcode:2010RMxAA..46..331A 
  4. ^ a b Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J 
  5. ^ a b Mermilliod, J. C.; Mayor, M.; Udry, S. (July 2008), "Red giants in open clusters. XIV. Mean radial velocities for 1309 stars and 166 open clusters", Astronomy and Astrophysics, 485 (1): 303–314, Bibcode:2008A&A...485..303M, doi:10.1051/0004-6361:200809664 
  6. ^ a b Nordgren, Tyler E.; et al. (December 1999), "Stellar Angular Diameters of Late-Type Giants and Supergiants Measured with the Navy Prototype Optical Interferometer", The Astronomical Journal, 118 (6): 3032–3038, Bibcode:1999AJ....118.3032N, doi:10.1086/301114 
  7. ^ Gray, R. O.; Graham, P. W.; Hoyt, S. R. (April 2001), "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. II. Basic Parameters of Program Stars and the Role of Microturbulence", The Astronomical Journal, 121 (4): 2159–2172, Bibcode:2001AJ....121.2159G, doi:10.1086/319957 
  8. ^ Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1), Bibcode:1970CoAsi.239....1B 
  9. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016. 
  10. ^ a b c Kaler, James B., "Mirfak", Stars, University of Illinois, retrieved 2012-03-14 
  11. ^ Ramanamurthy, G. (2007), Biographical Dictionary of Great Astronomers, Sura Books, p. 167, ISBN 81-7478-697-X 
  12. ^ Garrison, R. F. (December 1993), "Anchor Points for the MK System of Spectral Classification", Bulletin of the American Astronomical Society, 25: 1319, Bibcode:1993AAS...183.1710G, retrieved 2012-02-04 
  13. ^ Mérand, Antoine; et al. (August 2007), "Extended Envelopes around Galactic Cepheids. III. Y Ophiuchi and α Persei from Near-Infrared Interferometry with CHARA/FLUOR", The Astrophysical Journal, 664 (2): 1093–1101, arXiv:0704.1825Freely accessible, Bibcode:2007ApJ...664.1093M, doi:10.1086/518597 
  14. ^ a b c Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 331. ISBN 0-486-21079-0. Retrieved 2012-09-04. 
  15. ^ Davis Jr., G. A. (October 1944), "The Pronunciations, Derivations, and Meanings of a Selected List of Star Names", Popular Astronomy, 52 (3): 14, Bibcode:1944PA.....52....8D 
  16. ^ Pegasus
  17. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016. 
  18. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016. 
  19. ^ "Astronomer charts skies in Hawaiian" (PDF), Mālamalama, the Magazine of the University of Hawai'i System, 29 (2): 8, May 2004, retrieved 2012-03-14 
  20. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日